Joshua 22:11

‘ And the children of Israel heard it said, “See, the children of Reuben, and the children of Gad, and the half tribe of Manasseh, have built an altar before (at the frontier of) the land of Canaan in the circles of Jordan on the side that belongs to the children of Israel.'

Word about the building of the great altar quickly spread and reached the authorities. The resulting anger would not be because of where it was built but because of its presumed purpose, although in fact where it was built tended to indicate that it was not for ritual use, otherwise it would have been built on the eastern side.